1. Field of the Invention
This invention relates to dasher boards for skating rinks and more particularly to the mold, method of, and apparatus for forming backing shells for dasher boards of plastic sheet material and the method of making the dasher board itself.
2. Prior Art and Objects of the Invention
Applicant is unaware of any mold construction in the prior art such as that disclosed or a molding apparatus or method employing such a mold construction for making plastic backing shells for fiberglass dasher boards for skating rinks or any other object. The dasher boards capable of being formed with the backing made by the mold, method, and apparatus herein disclosed are shown generally in my U.S. Pat. No. 3,883,120 of May 13, 1975 entitled "Monolithic Dasher Board for Skating Rinks" and are essentially a waist-high retaining wall around the outer periphery of the rink when positioned vertically end to end. Heretofore, the dasher boards set forth in my afore-mentioned patent were made by placing numerous, successive layers of fiberglass and polyester resinous material directly on a positive mold coated with a release gel. After the resinous material had cured, the completed board could be removed from the mold. This method had the serious drawback that numerous positive molds had to be provided so that other boards could be in the process of being formed while others were curing. Such positive molds were very expensive. The backing shells of the present invention provide an inexpensive positive mold which becomes an integral part of each completed dasher board, thus speeding up production, reducing mold and material costs, and eliminating the necessity of a release gel.
The formation of plastic objects by drawing a heated plastic sheet into a negative mold is shown in U.S. Pat. No. 2,749,572 issued June 12, 1956. In this type of apparatus, the air is withdrawn from an area proximate to the molding surface through a plurality of small holes formed through the molding surface. Generally, the more holes present the more uniformly distributed the vacuum is and the better the heated plastic can be made to conform to the contours of the mold surface. This is particularly true when the objects are relatively small and the curved surfaces are gradual and not sharp. However, when the object to be formed is large such as a 4 by 8 foot dasher board for skating rinks which is basically a five sided, rectangular shaped box having sharply defined edges, the problems of constructing a mold to vacuum form such a board are considerable. Further, if parts of the mold itself must be capable of being removed so that the completed dasher board can be removed from the mold, the problem of providing a mold construction with the proper vacuum distribution is magnified. Applicant has discovered that by making all of the forming members loosely fitting within a vacuum box and providing a channel in the forming members for distributing the vacuum to the cracks formed between the forming members themselves as well as between the forming members and the vacuum box, a superior mold results and one which is particularly suited for use in a method and apparatus for molding large, rectangular shape, box-like objects.
It is therefore the primary object of the present invention to provide a novel mold construction, method and apparatus for vacuum forming backing shells for skating rink dasher boards and a novel method of making the dasher board itself.
It is another object of the invention to provide an apparatus and mold construction which is particularly suited to vacuum forming large objects having the walls thereof substantially perpendicular to each other.
It is a further object of the invention to provide an apparatus and a mold for use therewith which is uncomplicated in design and made of inexpensive materials.
It is a still further object of the invention to provide a method of making a complete dasher board for skating rinks.
The novel features which are believed to be characteristic of the invention both as to its organization and method of operation, together with further objectives and advantages thereof will be better understood from the following description considered in connection with the accompanying drawings in which a presently preferred embodiment of the invention is illustrated by way of example. It is to be expressly understood, however, that the drawing is for the purpose of illustration and description only, and is not intended as a definition of the limits of the invention.